Without the extra $900 to $1,000 a month Shanna Todd makes in her second job as a restaurant server, the 32 year-old consultant in Washington, D.C., would "be barely making it."

After losing her job as a sales manager when her company closed during the recession, working two years in South Korea led Todd to make a career change. But that meant heading back to school, and starting from the bottom in a new field.

"I wouldn't be able to finish my masters, and I wouldn't be able to probably pay my bills," Todd says of what life would be like without her additional income. Todd estimates she's making the equivalent of a $28,000-a-year salary in hourly wages from her consulting job with an international development organization.

Across the country, single women feel worse than both men and any age group about their ability to make ends meet. In a survey of 1,200 adults given exclusively to USA TODAY by Consumers' Research, the data show that about 60% of single women say they don't earn enough to cover their expenses.

That's compared with 45% of everyone surveyed, and 57% of those ages 50 to 59, the group with the highest percentage who said they don't make enough to cover expenses.

Do Americans not make enough money, or are they living beyond their means?

"I would say that those two are the same thing," says Joe Colangelo, executive director of Consumers' Research. "If you aren't making enough to support your lifestyle, you need to make some life and habit changes."

Some women see it differently. They earn 77 cents, on average, for every dollar men make. As Millennials seek a fulfilling social life and meaningful career, they're taking on additional work to afford that lifestyle.

Gabrielle Nicolini, 31, works as an account manager for a non-profit in Atlanta. Even though she's in a salaried position — she says she makes in the upper $40,000-range — she still works about six hours a week at a restaurant for extra income. The cash from that job, about $300 a month, goes toward emergency expenses and being able to go out with friends.

"The majority of my money is earmarked to bills," she says, and at $750 a month, her biggest expense is rent. Nicolini says she's been living paycheck-to-paycheck since graduating college in 2005.

While she says she'd be able to cover her basic expenses without the second job, emergency situations would put her cash flow in jeopardy.

"If I had an emergency, I would kind of be in trouble," she says. "I just also want to maintain the lifestyle I enjoy." That includes being able to go out to dinner with friends and to pay for vacations.

Todd also says she's held two jobs since graduating from college in 2005. Both she and Nicolini are single.

"I can't seem to make enough money in the one job to pay for all my expenses wherever I'm living," Todd says.

While 21% of those surveyed said they have a household income of more than $100,000 a year, the majority of 18-to-29-year-olds, 19% of those surveyed, said they have a household income of less than $20,000 a year, though 22% of that age group said they weren't employed. The 30-to-39 year-old age group had the highest number of people making more than $100,000 a year, at 27% of respondents.

While Colangelo doesn't want to draw definitive conclusions about whether the data truly reflect pay discrepancies or just Americans' tendency to live beyond their means, he says, "whether it's perceived or real, that half of Americans think that they aren't taking in enough to cover what is going out is a huge problem."